The present invention relates generally to automatically controlled cutting equipment of the type used to generate multiple pattern pieces from a lay-up of sheet material. More particularly, the present invention deals with apparatus for automatically positioning a top ply label applicator at a desired elevation or distance above the surface of the top ply of sheet material to apply information labels to stacks of pattern pieces cut from the lay-up.
It is well known in the cutting of sheet material, particularly limp sheet material such as cloth, to use computer assisted means to produce a marker indicating the shapes and arrangements of parts to be cut from a quantity of work material. The information inherent in the marker is then processed in combination with ancillary input data to provide a set of marker instructions or a drawn marker, usable by a cutting system. The cutting system generally includes means for spreading a single sheet, or a lay-up of sheet material to be cut and an automatically controlled cutting machine using the marker instructions or a manually controlled cutting machine using the drawn marker as a pattern for cutting the spread material into the desired shapes. The cutting system also generally includes a labeller of some type, to apply identification labels to the top surface of the work material, either before or after the cutting, to identify the parts cut from the material. In cases were the work material is a lay-up of sheets, each part cut from the material actually consists of a stack of individual pieces. An apparatus and method for making a marker representation is shown, for example, in U.S. Pat. No. 3,887,903. Labelling devices for use with sheet material cutting systems are shown by U.S. Pat. Nos. 4,028,186; 4,189,337 and 4,514,246. As evident from the referenced patents, the labeller is mounted either on the same carriage as a cutting head or on the carriage of the spreader to control the positioning and operation of the labeller through the same controller as used to control the cutting head or spreader. A labelling apparatus wherein the apparatus is a unitary self-driven and self-controlled module capable of easy transfer from one point of use to another without requiring control cabling and connection to separate control equipment is disclosed in a pending U.S. patent application Ser. No. 585,711, filed Sep. 19, 1990 and titled "Labelling Apparatus and Method for a Sheet Material Cutting System and a Supply of Labels for Use Therewith" and assigned to the same assignee as the present invention.
Typically, the height of the lay-up of sheet material spread varies along the length of the lay-up for the reason that the number of sheets spread is different to accommodate the different number of plies associated with the various different patterns identified by the marker. Generally, the sheet material is spread to produce decreasing heights along the length of the lay-up but may also be spread to produce increasing heights along the length of the lay-up. Therefore, the elevation of the labeller above the top ply along the lay-up must be continually adjusted to accommodate the different ply heights so that the labeller apparatus may properly apply the identification label to the top ply of the stack to be identified. Accordingly, the rate of label application and output of the work pieces is significantly reduced due to the continual readjustment of the labeller above the top ply during the cutting and labelling processes.
It is a general aim of the present invention therefore to provide an improved labeller apparatus which automatically adjusts its elevation above the top ply surface of a lay-up of sheet material to accommodate ply height variations along the length of the lay-up.